重组竹的顺纹拉压强度与本构关系

Uniaxial strength and constitutive law of parallel strand bamboo

重组竹是由原竹经一定生产工艺制作得到的一种高强竹质复合材料,研究重组竹材料的纵向单轴本构关系,是建立此类材料本构关系进行重组竹基本构件非弹性分析的基础。笔者在将重组竹理想化为横向各向同性材料的基础上,研究了重组竹材料纵向受拉与受压破坏形态,建立了重组竹材料纵向应力-应变关系解析公式。结果表明:重组竹受拉破坏缘于纵向纤维被拉断,呈脆性断裂破坏形态;受压破坏缘于破坏面附近纵向纤维压屈,破坏分纵向屈曲破坏、压剪破坏和纵向劈裂破坏3种形态;重组竹的受拉应力-应变曲线呈线性关系;当压应力小于比例极限时,受压应力-应变关系为直线,当压应力超过比例极限后,应力-应变关系呈非线性强化特征,非线性段的应力可以表达为应变的二次函数。

Parallel strand bamboo（ PSB） fabricated through industrial process using raw bamboo is a high strength bamboo-based composite,and it has extensively potential prospective use as a structural material for building construction.To study the longitudinal stress-strain relationships of this material is a fundamental work to build the constitutive relation of PSB and to conduct the inelastic analysis for PSB structural members. For this reason,this paper investigated the failure mode of tension and compression of PSB in longitudinal direction firstly by test,and then the damage mechanisms of this material were studied. Finally,the analytical stress-strain formula of PSB composite was suggested. The results showed that parallel-to-grain tensile failure of PSB composite was due to the breaking of longitudinal fibers and shown brittle characteristics. The compressive failure was contributed to the bulking of the fibers near the damage area,which has 3 types of failure modes including,longitudinal bulking failure,compressive-shearing failure,and slip failure in longitudinal direction. The stress-strain relationship in longitudinal direction of PSB composite exhibits linear behavior in tension; and in compression. It remains in linear form within the proportional limit,and it can also be simulated by quadratic polynomial,even the stress exceeds the limit.